Image color Gamut is an area that is defined by a certain quantity of colors. Different displays have different color gamut ranges. The internationally accepted color measurement standard is the color gamut range specified by National Television Standards Committee (NTSC, US), namely, the color range that can be presented in display. The color range that each TV set can deal with is related to the technology used for producing the TV set. International Lighting Association (CIE) has developed a CIE-xy chromaticity diagram which is used to describe the color gamut. In the diagram, the range of the triangle formed by connecting the RGB three points represents the color gamut ranges of various display devices, and the larger the area of the triangle is, the larger the color gamut range of the display device is. As shown in FIG. 1, the black triangle represents the source end, and is generally recorded as BT.709 in displays. The white area represents the display end. For different displays have different display ranges, the areas of the triangle are also different. The larger the triangle is, the broader the display range is.
Color gamut retaining of images refers to that the color gamut of the source end is displayed within the color gamut of the display end, and the range of the color gamut finally displayed on the display is the range of the color gamut of the source end. As shown in FIG. 1, the coordinates of the RGB three points of the source end are retained and displayed within the range of the color gamut of the display end. At present, the method for retaining color gamut of image is, as shown in FIG. 2, the RGB color gamuts of the source end and the display end are converted to XYZ color gamut respectively; the XYZ color gamut of the display end corresponding to the XYZ color gamut of the source end is inquired; then the inquired XYZ color gamut of the source end is converted back to the RGB color gamut by an inverse matrix; finally, the result is outputted.
Currently, the RGB values of each pixel needs to be converted to XYZ at the time point the RGB values are imputed, then XYZ of the display end is inquired, and the inquired XYZ is finally converted back to RGB. When the image imputed is a large image, the RGB values corresponding to each pixel need to be calculated, thus it would take a lot of time to generate a new image, resulting in a waste of time and a consumption of CPU. Therefore, the computational efficiency is low.